[ObjC ARC] Converts ios/chrome/test/ocmock:ocmock to ARC.

ios/chrome/test/ocmock/OCMockObject+BreakpadControllerTesting.mm

Index: ios/chrome/test/ocmock/OCMockObject+BreakpadControllerTesting.mm
diff --git a/ios/chrome/test/ocmock/OCMockObject+BreakpadControllerTesting.mm b/ios/chrome/test/ocmock/OCMockObject+BreakpadControllerTesting.mm
index df3cc83da374062d680eec1aa6f1088a22f5995f..ba86516207823738a3d5b24d107496547c162ca4 100644
--- a/ios/chrome/test/ocmock/OCMockObject+BreakpadControllerTesting.mm
+++ b/ios/chrome/test/ocmock/OCMockObject+BreakpadControllerTesting.mm
@@ -8,11 +8,15 @@
 #include "testing/gtest/include/gtest/gtest.h"
 #import "third_party/ocmock/OCMock/OCMock.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 @implementation OCMockObject (BreakpadControllerTesting)
 
 - (void)cr_expectGetCrashReportCount:(int)crashReportCount {
   id invocationBlock = ^(NSInvocation* invocation) {
-    void (^block)(int);
+    __unsafe_unretained void (^block)(int);
     [invocation getArgument:&block atIndex:2];
     if (!block) {
       ADD_FAILURE();